The present invention relates to self-contained toilet systems, and, more particularly, to self-contained, vacuum-assisted toilet systems for use in vehicles in general and aircraft, in particular.
Self-contained toilet systems have been utilized in vehicles for many years and are currently in use in aircraft, buses and trains, as well as in recreational vehicles of all sorts. For many years, recirculating systems have been widely accepted because, among other things, they did not require extensive stores of flushing fluid and did not require that substantial amounts of flushing fluid be retained with the waste products.
Vacuum-assisted toilet systems have been described in references as early as 1895. A series of patents issued to S.S Riegel from applications filed Apr. 28, 1925, U.S. Pat. Nos. 1,613,848; 1,613,849; and 1,619,369. These patents described a self contained, vacuum assisted toilet system for a railway passenger car. The system utilized a bowl, a compressed air ejection system for transferring the waste from the bowl to a waste tank in which a partial vacuum was maintained, either through the use of an exhaust fan or through the use of a compressed air system which operated on the principal of an aspirator.
In more recent years, James M. Kemper described a vacuum assisted recirculating toilet for use in aircraft in U.S. Pat. No. 3,922,730, which issued Dec. 2, 1975. A plurality of individual recirculating toilet units were commonly connected to a waste tank which was vented to the exterior of the aircraft through a pressure regulator. The fluid in the tank was withdrawn by a pumping system for flushing purposes. However, each toilet, when operated, transported its waste matter through conduits under the influence of a partial vacuum in the waste tank.
A comparable system was disclosed in the patent to Raymond J. Carolan, U.S. Pat. No. 4,063,315, issued Dec. 20, 1977. Carolan provided a blower unit to provide the partial vacuum when the aircraft was on the ground or at altitudes insufficient to provide the partial vacuum required for efficient operation of the system. This system, too, was a recirculating system which withdrew fluid from the waste tank to be used as flushing fluid.
In order to avoid the problems that are associated with recirculating toilet systems, including the aesthetic questions that arise from the repeated use of recirculated waste fluids, several systems have been proposed which utilize the fresh or potable water supply of the vehicle. Because such a system requires that the water thus used be stored while the vehicle is in transit, it is desirable to minimize the volume of water that is to be used at each operation of the toilet system. The other constraint, of course, is the limited amount of potable water that can be carried between servicing stops of the vehicle.
One such system was shown in the patent to Badger et al, No. 4,275,470, which issued June 30, 1981. That system employed a holding tank which was maintained at a vacuum. As the toilet was used, a fresh water source supplied a limited volume (eight ounces) of water to flush the toilet. A flush valve is opened and a pressure differential is created between the toilet bowl and the holding tank sufficient to propel the waste to the tank. For operation when the pressure external to the vehicle is not sufficiently low to create and adequate differential, a vacuum blower is employed to assist in creating the desired differential.
A similar system was disclosed by Iwans in U.S. Pat. No. 4,376,314, issued Mar. 15, 1984. Iwans taught a toilet that could be sealed from the surrounding environment and which provided an air manifold in addition to the flushing fluid source so that a combination of high velocity air and water could be used to flush the waste products into a conduit to the waste tank, which is maintained at a vacuum. This system also utilizes approximately eight ounces of water for each flush operation.
An aircraft system employing a plurality of toilets feeding into a common holding tank was disclosed by Chen et al in U.S. Pat. No. 4,521,925, issued June 11, 1985. In that patent, the holding tank was maintained at a vacuum, either by communication with the exterior of the vehicle while at altitude or through the use of a vacuum blower when the external environment does not provide a sufficient pressure differential. A specially designed bowl and manifold structure introduces the water in a plurality of streams which permit the efficient use of approximately eight ounces of fresh water for each flush operation. A liquid separator is provided so that entrained air can be vented to the exterior while preventing the flow of moisture.
Systems of the prior art such as those taught in the above mentioned patents require that the main storage tanks be sufficiently strong to withstand the pressure differential that exists between the interior and exterior of the tank inasmuch as the tanks are usually located within the pressurized portion of the aircraft. This generally requires a pressure vessel which usually takes on a spherical or cylindrical shape with hemispherical ends. These shapes must be placed in an otherwise unobstructed volume of the aircraft hull.
Further, if the toilet system is to be available to passengers while the aircraft is on the ground, the vacuum blower system must be energized to evacuate the tank, each time a toilet is flushed. This may require that the blower system be continuously in operation during any period that the aircraft is on the ground and occupied by passengers.
A water saving commode patented by Joyce A. Russell on Jan. 6, 1981, U.S. Pat. No. 4,242,765, disclosed a device intended for domestic use that included an interim holding tank that, when sufficient wastes had accumulated, dumped the wastes into a sewer line. Adapting the Russell system to a vehicle, such as an aircraft, provides a flexibility of use that enables operation under conditions where a vacuum is not readily available.
It would be desirable, to have a nonrecirculating, vacuum assisted toilet system that was sufficiently simple and otherwise inexpensive and which could utilize a waste tank that could be fitted anywhere within the pressurized volume of the aircraft. If a pressure vessel is not required, the tank may have an irregular shape, permitting installation in any location having sufficient available volume.
In an alternative embodiment, a system that did require a pressure resistant waste storage tank could be provided. It would also be desirable to have a system that could function while the aircraft was on the ground and yet did not require the creation of a vacuum throughout the system each time the toilet was used.